[BRENT in 10-uh-C]

Terry, you have too many variables in what you are telling us here for any of us to give you accurate advice. First off, 375 is an epoxy, -which in my opinion is not what you need to be going with but your car/your way. Epoxy does not sand well. Look for an urethane or synthetic high-build primer instead.

It is possible that water was present however you generally can see if bead up just like water. Based on your saying pimples & blisters, I am going to say it probably has more to do with the solvents you are using. Most of those cheaper lines of paint use bizarre types of solvents such as acetone, naphtha, etc., -but they don't work with thinner or reducers. Also, most of those cheap epoxies have a cross-link time of 15-30 minutes between the time it is mixed until the time you can spray it. Did you wait the prescribed amount of time??

As far as it coming out rough, You did not mention what type of gun or what tip size. Knowing that helps us know what cap pressure to use. The idea is to use enough pressure to properly atomize (bust-up the paint) where it can lay down smoothly. I would probably use a 1.6 cap on a HVLP gun with approximately 10 PSI at the cap. Depending on the gun, this will probably be 30-40 PSI where it enters the gun to keep the volume there. A smaller cap will require less gun pressure to maintain that cap pressure. You also need to check the recoat window on that paint as some of those can be around 48 hours.